Emergency surgery of the gastrointestinal tract - Part 1
Emergency gastrointestinal surgery presents the clinician with several challenges. Animals may present with severe dehydration and cardiovascular instability secondary to frequent vomiting, fluid sequestration in the bowel, or bowel perforation causing peritonitis and sepsis. Vomiting or regurgitation may result in aspiration pneumonia. During initial resuscitation, the clinician must determine the nature of the problem and decide if surgery is indicated. The animal must be as stable as possible before anesthesia. However, it is important to realize that complete stabilization of the animal may not be possible until the underlying disease (for example, peritonitis) is addressed. Anesthetic agents with minimal depressant effects on the cardiovascular and respiratory systems are used. The entire ventral abdomen and caudal thorax are clipped and prepared for aseptic surgery. Broad spectrum, bacteriocidal antibiotics are administered if bacterial contamination of the peritoneal cavity is suspected or anticipated. A large incision is made, extending from the xiphoid caudally past the umbilicus. A complete exploratory laparotomy is performed and all organ systems examined sequentially. Definitive treatment depends on the organ system affected and the nature of the disease.
During surgery, the clinician must do a complete abdominal exploratory and not focus on one obvious lesion. Emergency gastrointestinal surgery requires critical evaluation of bowel viability and exacting technical skill for the best clinical outcome. Adept postoperative management is vital, including careful physiologic monitoring, an index of suspicion for potential complications, and appropriate nutrition.
Esophageal foreign bodies should be suspected in any animal presenting with a history of regurgitation. They tend to lodge at points of narrowing in the esophagus: the thoracic inlet, he heart base, and just cranial to the caudal esophageal sphincter. Esophageal foreign bodies should be treated as emergencies. Contraction of the esophageal muscles around a foreign body worsens mucosal ischemia and makes esophageal perforation more likely. In most cases, non-surgical removal should be attempted initially. However, endoscopic removal of thoracic esophageal foreign bodies is contraindicated in animals with evidence of esophageal perforation. In these animals, insufflation of the esophagus with air from the endoscope to manipulate the foreign body leads to immediate tension pneumothorax and severe cardiorespiratory compromise. Animals with esophageal perforation do not always have radiographic evidence of pneumothorax or pneumomediastinum. A mild pleural effusion may be the only sign of esophageal perforation on plain thoracic radiographs. Contrast radiography should be performed in cases in which the diagnosis of perforation is in doubt.
In the majority of cases, endoscopy can be used to remove esophageal foreign bodies. A rigid or flexible endoscope is passed to the level of the foreign body and air insufflated through the endoscope to distend the esophagus away from the foreign body. The foreign body is either grasped and removed, or in cases of foreign bodies in the distal esophagus, gently moved into the stomach. The esophagus is then redistended and inspected for any mucosal tears. Full thickness tears in the esophageal wall necessitate immediate surgical repair.
Surgery is performed when foreign bodies cannot be removed by endoscopy. The approach is dictated by the foreign body's location. Foreign bodies lodged in the cervical esophagus are approached via a ventral midline cervical incision. Foreign bodies lodged at the level of the heart base are approached through a right lateral fourth intercostal thoracotomy to avoid the aorta. Foreign bodies in the caudal thoracic esophagus are approached through a left seventh or eighth space intercostal thoracotomy; foreign bodies in the distal esophagus can sometimes be retrieved by manipulation through a gastrotomy incision. A longitudinal esophagotomy is performed. The esophageal wall in the area of the foreign body is checked for perforation, and the incision closed with single interrupted, appositional sutures of 3/0 or 4/0 polydioxenone (PDS).
Esophageal resection is occasionally required when pressure from a foreign body has caused substantial transmural esophageal necrosis. The esophagus is dissected completely free of the mediastinum in the area of the perforation. The visceral pleura of the lung is often also adhered to the area of esophageal perforation. The esophagus is mobilized proximal and distal to the perforated area, the necrotic tissue resected (Figure 1) and the healthy ends sutured with a single layer of appositional sutures of 3/0 or 4/0 PDS (Figure 2). A flank laparotomy is performed to mobilize the omentum, which is passed through a small incision in the diaphragm and wrapped around the anastomotic site. A feeding tube is also placed into the stomach for postoperative nutrition.
Gastric dilatation/volvulus (GDV) is a range of syndromes varying from severe gastric distension without volvulus, to volvulus without distension. Massive distension of the stomach with swallowed food or air results in obstruction of the portal vein and caudal vena cava. Decreased venous return from these vessels results in severely decreased cardiac output and poor tissue perfusion. Ischemia affects the heart, resulting in arrhythmias, and the stomach, causing necrosis in severe cases. Many GDV dogs have disseminated intravascular coagulation (DIC) and are endotoxemic.
Resuscitation with shock doses of crystalloids (or initially hypertonic saline/dextran) prior to anesthesia and surgery is vital. Additional therapies, such as free radical scavengers (for example, desferoximine) have potential, if not proven clinical benefits. Once resuscitation is underway, the stomach is decompressed by carefully passing an orogastric tube or, if this is not possible, gastric trocharization. Radiographs are made with the dog in right lateral recumbency to differentiate dilatation from volvulus (Figure 3). There are now somewhat conflicting reports on the prognostic significance or preoperative ventricular arrhythmias (1,2). It is clear however that preoperative lactate levels of >6 mM/L are associated with a worse prognosis and a greater likelihood of gastric necrosis (3).
At surgery, the stomach is decompressed, derotated, and replaced in a normal position. The spleen is exteriorized and examined for viability, venous or arterial thrombosis, and short gastric vessel rupture. A splenectomy is performed if necessary. The remainder of the abdomen is explored, and then the stomach is re-examined for necrosis, particularly along the greater curvature. As a guide, areas of the stomach which are discolored, a dark purple or grey/green, which feel paper thin, or do not bleed when incised must be removed. If there is doubt concerning the viability of an area it should be removed, using either a stapling device (TA 90 stapler, 4.5 mm cartridge) or manual resection and suturing. A permanent gastropexy is performed; the author uses a tube gastropexy to allow for postoperative gastric decompression, but at least seven other "pexy" techniques are described. The abdomen is copiously lavaged and closed.
Postoperatively, GDV patients require intensive care and monitoring. The rate of intravenous fluid administration is based on an assessment of perfusion. Tissue perfusion is estimated from clinical examination, blood pressure and urine output measurements, and laboratory parameters. Cardiac arrhythmias often develop in the first 24 to 48 hours after surgery. They are not necessarily associated with a poor prognosis as previously thought. Antiarrhythmic therapy is given if the abnormality is associated with poor cardiac function (subjectively assessed from mucus membrane color, heart rate, and arterial blood pressure) or severe electrical disturbance (R on T phenomena).
Most gastric foreign bodies are not true surgical emergencies. However, needles should be removed as soon as possible to prevent migration or perforation. In most cases, this is readily accomplished using a flexible endoscope.
Occasionally, severe gastric ulceration and bleeding can be successfully treated surgically. Gastric ulceration and hemorrhage are associated with gastric neoplasia, mast cell tumors, gastrinomas, stress, and exogenous corticosteroids. However, cases of severe hemorrhage occur most frequently after ingestion of non-steroidal anti-inflammatory medication. Surgery is considered for those cases with massive bleeding in which medical therapy fails. The animal is stabilized with transfusions of packed red blood cells and plasma. Rapid endoscopy is vital to differentiate focal hemorrhage that may be amenable to surgical treatment from diffuse gastric ulceration and hemorrhage. The peritoneal cavity is explored, a large gastrotomy incision made, and the stomach mucosa examined. Focal bleeding ulcers are resected.
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